Drilling fluid

ABSTRACT

AN AQUEOUS DRILLING FLUID DISPRESANT AND A METHOD OF DRILLING WELLS USING SAID DRILLING FLUID DISPERSANT WHICH CONTAINS AN ARYL SUBSTITUTED ALIPHATIC ACID COMPOUND AS THE DISPERSANT, NAMELY A B-3,4-DIHYDROXYPHENYL PROPIONIC ACID ALKALI METAL SALT THEREOF OR MIXTURES THEREOF.

3,682,821 Patented Aug. 8, 1972 3,682,821 DRILLING FLUID Jack H. Kolaian, Wappingers Falls, N.Y., assignor to Texaco Inc., New York, N.Y.

No Drawing. Filed Dec. 24, 1969, Ser. No. 888,052 The portion of the term of the patent subsequent to Feb. 8, 1989, has been disclaimed Int. Cl. Cm 3/20, 3/14 US. Cl. 252-85 C 16 Claims ABSTRACT OF THE DISCLOSURE An aqueous drilling fluid dispersant and a method of drilling wells using said drilling fluid dispersant which contains an aryl substituted aliphatic acid compound as the dispersant, namely a 18-3,4-dihydroxyphenyl propionic acid alkali metal salt thereof or mixtures thereof.

This invention relates to a novel aqueous drilling fluid for drilling wells through sub-surface formations by means of well drilling tools, and particularly to such an aqueous well drilling fluid having improved dispersibility as a result of containing therein a novel dispersant as hereinafter more fully described. The invention is also concerned with a method of drilling wells employing the novel aqueous drilling fluid.

Drilling fluids, or muds as they are sometimes called, are slurries of clayey solids used in the drilling of wells for tapping underground collections of oil, gas, brine or water. Such fluids have a number of different functions, the most important of which are to assist in the removal of cuttings from the well, to seal off formations of gas, oil, or water which may be encountered at different levels, to lubricate the drilling tool and drill pipe which carries the tool, and to hold the cuttings in suspension in event of shut-downs in drilling.

An ideal drilling fluid is a thixotropic colloidal system, i.e., a fluid which on agitation or circulation (as by pumping or otherwise), has a measurable relatively low viscosity and is free flowing (not plastic), particularly at high temperatures; but when such agitation or circulation is halted, the fluid sets or gels. The rate of gel formation is such as to permit the cuttings to fall only a short distance before the gel structure is sufficiently strong to support them.

When such a driling fluid having the proper viscosity, the proper gel rate and proper gel strength is circulated through a well bore, it has a sufficiently high viscosity to carry the cuttings and sand from the bottom of the hole to the surface and it has a gel rate such as to allow the cuttings and sand to settle in a settling pit. On standing in a quiescent state, it develops sufiicieut gel strength to prevent the settling of the cuttings, sand or weighting material, etc., in the well bore when it becomes necessary to discontinue circulation for any appreciable period of time. Such a fluid is also characterized by its ability to form a mud cake on the borehole wall, thereby assisting in sealing off the traversed formations and inhibiting so-called water loss, i.e., loss of water from the drilling fluid.

One of the principal problems in mud chemistry is the production of suitable drilling fluids having satisfactory dispersibility, and the necessary thixotropic properties discussed above.

In accordance with the present invention the problems of dispersibility in aqueous drilling fluids can be solved by incorporating in an aqueous drilling fluid a aryl substituted aliphatic acid or an alkali metal salt thereof or mixtures thereof.

More particularly preferred aryl substituted aliphatic acid compounds of the present invention include fi-3,4- dihydroxyphenylpropionic acid, the sodium and potassium salts and mixtures thereof.

It is known from the article appearing in Zhur. Priklad. Khim. 35, pages 638-647 (1962), Organic Viscosity Reducers in Clay Solutions by D. Tischenko and S. Fleisher (CA, 57, 2491g, 1962), that the ortho-dihydroxybenzenesulfonic acids, the ortho-dihydroxy-alphatoluenesulfonic acids and Water soluble salts thereof are viscosity reducing agents in clay laden drilling fluids whereas the corresponding metaand paradihydroxybenzenes including the corresponding sulfonic acid derivatives and water soluble salts thereof are ineffective viscosity reducing agents for aqueous drilling fluids.

The aryl substituted aliphatic acid compounds of the present invention may be added to an aqueous drilling fluid in amounts ranging from about 0.1 pound to about 10 pounds per barrel of drilling fluid. In general, it has been found that amounts less than 0.1 pound per barrel do not produce completely satisfactory results in terms of dispersing activity whereas amounts above about 10 pounds per barrel are economically unattractive and no improved results are obtained therewith. A preferred range for the aryl substituted aliphatic acid compounds of the present invention is from about 0.25 to about 5 pounds per barrel of drilling fluid for most consistent results and efliciency.

The aryl substituted aliphatic acid compounds employed in the present invention are known compounds and the manner of their preparation is known in the art.

In the table, gel strength (Gels) is reported as determined by a shearometer in accordance with the procedure in the American Petroleum Institute publication RP-29, results being expressed either as pounds/ 100 square feet or as time in seconds for a tube to settle in the mud (after the mud has stood for zero time and for 10 minutes). If it settles in more than seconds, shear is reported as pounds per hundred square feet. Yield Point (YP) is calculated by subtracting the Plastic Viscosity (PV) from the Fann Viscosity reading at 300 r.p.m. Plastic Viscosity (PV) is obtained by calculation, subtracting the Faun reading at 300 r.p.m. from the 600 r.p.m. reading. Apparent Viscosity (AV) is equal to one-half of the Fann 1 Low pH mud.

2 Modified shale control mud (without a calcium salt). A=B 3,4-dihydroxyphenyl propiouic acid.

Viscosity reading obtained at 600 rpm. The fluidity of a mud can be back calculated from these data, the results being expressed in Farm Viscosity at 600 rpm. and 300 r.p.m. for a direct reading viscosimeter.

The properties of the base mud are shown in the table.

The test data set forth in the preceding table indicate the advantages of the aryl substituted aliphatic acid compounds as the dispersants of the present invention in aqueous drilling fluids and demonstrate the beneficial results of same in improving the dispersibility of drilling fluids.

Representative physical properties of the drilling fluids both before and after addition of the aryl substituted aliphatic acid compounds of the present invention are shown in the table. In each example the amount of material or materials added to the base muds, if any, are shown, expressed in terms of pounds of material per barrel of drilling fluid.

The data in the above table show that the aryl substituted propionic acid compounds of the present invention are effective dispersants for aqueous drilling fluids.

In the above table, the expression Modified Shale Control Mud refers to an aqueous drilling fluid designed for use in drilling through heaving shale containing clay solids and lime or calcium hydroxide but without calcium chloride.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. An aqueous drilling fluid containing clay solids and as the dispersant an aryl substituted aliphatic acid, selected from the group consisting of B-3,4-dihydroxyphenylpropionic acid, the alkali metal salts and mixtures thereof, said aryl substituted aliphatic acid compound being present in the drilling fluid in an amount suflicient to impart a reduced viscosity thereto.

2. An aqueous drilling fluid as claimed in claim 1 wherein the aryl substituted aliphatic acid compound is fl-3,4-dihydroxyphenylpropionic acid.

3. An aqueous drilling fluid as claimed in claim 1 wherein the aryl substituted aliphatic acid compound is sodium B-BA-dihydroxyphenyl propionate.

4. An aqueous drilling fluid as claimed in claim 1 wherein the aryl substituted aliphatic acid compound is potassium B-3,4-dihydroxyphenyl propionate.

5. An aqueous drilling fluid as claimed in claim 1 wherein the aryl substituted aliphatic acid compound is a mixture of ,8-3,4-dihydroxyphenyl propionic acid and sodium fl-3,4-dihydroxyphenyl propionate.

6. An aqueous drilling fluid as claimed in claim 1 wherein the aryl substituted aliphatic acid compound is a mixture of 5-3,4-dihydroxyphenylpropionic acid and potassium B-3,4-dihydroxyphenyl propionate.

7. An aqueous drilling fluid as claimed in claim 1 wherein the aryl substituted aliphatic acid compound is present in the drilling fluid in an amount of from 0.1 to 10 pounds per barrel of drilling fluid.

8. An aqueous drilling fluid as claimed in claim 7 wherein the aryl substituted aliphatic acid compound is present in the drilling fluid in an amount of from 0.25 to 5 pounds per barrel of drilling fluid.

9. In a method of drilling wells wherein the drilling fluid is passed through the well in contact with an earth formation during the drilling operation, the improvement which comprises contacting said earth formation with an aqueous drilling fluid containing clay solids and at least 0.1 pound per barrel of drilling fluid of an aryl substituted aliphatic acid compound as the dispersant selected from the group consisting of 8-3,4-dihydroxyphenylpropionic acid, the alkali metal salts and mixtures thereof, said substituted arylaliphatic acid compound being present in the drilling fluid in an amount suflicient to impart a reduced viscosity thereto.

10. In a method of drilling wells as claimed in claim 9 wherein the aryl substituted aliphatic acid compound is [3-3,4-dihydroxyphenylpropionic acid.

11. In a method of drilling Wells as claimed in claim 9 wherein the aryl substituted aliphatic acid compound is sodium fl-BA-dihydroxyphenyl propionate.

12. In a method of drilling wells as claimed in claim 9 wherein the aryl substituted aliphatic acid compound is potassium B-SA-dihydroxyphenyl propionate.

13. In a method of drilling wells as claimed in claim 9 wherein the aryl substituted aliphatic acid compound is a mixture of ,8-3,4-dihydroxyphenyl propionic acid and sodium ;8-3,4-dihydroxyphenyl propionate.

14. In a method of drilling wells as claimed in claim 9 wherein the aryl substituted aliphatic acid compound is a mixture of 5-3,4-dihydroxyphenylpropionic acid and potassium fl-3,4dihydroxyphenyl propionate.

15. In a method of drilling wells as claimed in claim 9 wherein the aryl substituted aliphatic acid compound is present in the drilling fluid in an amount of from 0.1 to 10 pounds per barrel of drilling fluid.

16. In a method of drilling wells as claimed in claim 10 wherein the aryl substituted aliphatic acid compound is present in the drilling fluid in an amount of from 0.25 to 5 pounds per barrel of drilling fluid.

References Cited UNITED STATES PATENTS HERBERT B. GUYNN, Primary Examiner U.S. Cl. X.R. 252356 

